An automobile is a self-propelled passenger-carrying vehicle
designed to operate on ordinary highways and usually supported
on four wheels. Power is provided in most modern cars by an
internal combustion engine fuelled
by gasoline (vaporized and premixed with a suitable quantity
of air). This is ignited in the (usually 4, 6, or 8) cylinders of the engine by spark plugs, fired in the appropriate sequence.
The gas supply and thus the engine speed is controlled from
the accelerator pedal. The driving power is communicated to
the road wheels through the transmission which includes a clutch (in the case of a manual transmission), enabling
the driver to disengage the engine without stopping it, a
gearbox (allowing the most efficient use to be made of the
engine power), various drive-shafts (with universal joints), and a differential which allows the driving wheels to turn
at marginally different rates in cornering.
Steering is controlled from a hand wheel which moves a transverse
tie rod mounted between the independently-pivoted front
wheels. Brakes of various types are mounted on all wheels,
an additional parking-brake mechanism being used when stationary.
In modern automobiles service brakes and steering may be power-assisted
and the transmission automatic rather than manually controlled
with a gearshift (see automatic transmission).
Although the first propelled steam vehicles were built by
the French army officer Nicholas-Joseph Cugnot in the 1760s,
it was not until Karl Benz and Gottlieb Daimler began to build gasoline-powered
carriages in the mid-1880s that the day of the modern automobile
dawned. The Duryea brothers built the first US automobile
in 1893 and within a few years several automobile manufacturers,
including Henry Ford, had started into business. The Ford
Motor Company itself was founded in 1903, pioneering the cheap
mass-market auto with the Model T of 1908. The automobile
industry expanded fitfully until the 1960s, improving automobile
performance, comfort, and styling, but more recently has been
forced to pay more attention to safety, environmental factors,
and energy conservation. Aerodynamics,
more efficient engines, and better transmission have been
the focus of development.
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